Process of ink or stain erasure



S-IO? PIP UNITED STATES QUGI DH HUUHI PATENT OFFICE PROCESS OF INK OR STAIN ERASURE Kenneth W. McPherson, Palmyra, N. Y., assignor to The Carters Ink Company, Cambridge, Mass, a corporation of Massachusetts No Drawing.

Application March 25, 1936,

Serial No. 70,904

4 Claims.

Pa er, although applicable to cloth a nd other materials.

Heretofore chemical ink and stain erasers for sized paper have harmed the sizing in the paper so that when the paper is again written on in ink at the place of the erasure, the writing is not easy, the ink will not take its natural color on the paper, and the lines will be more or less fuzzy.

The object of the invention is to avoid these difiiculties by not only removing the ink, or stain, from the paper, but otherwise so treating the paper that writing in ink upon it where the stain has been removed will be easy, the ink will take its natural color, and will exhibit sharply defined lines corresponding with the other writing, or ink, upon the paper.

The object of the invention is attained by a process in which erasure of the ink, or stain, will be accompanied with an effect or result that will cure any harm that has been done to the sizing in the paper by the erasure, and this by filling, or loading the paper with a precipitate which will take the place of the sizing that has been removed.

The process comprises steps in which chemical solutions are applied to the paper. The first step consists in the application to the paper of a chemical solution, of which the following is the preferred formula:

Water to make a 100% total.

In this formula the aluminum sulphate is used in order that the pr e cipitate aluminum hydroxide may be formed from it 153; the second step ofth e process, as will later be referred to, for filling, or loading the paper and replacing massing; t: een removed, 'or at least harmed by the apphcatio nof the first solution.

Other aluminum salts might be used, ammonium alum, especially, is good. Aluminum double sulphates, which include the alums, might be used, but inasmuch as they contain an added substance they should be used in larger proportions (about 9%) to bring up the needed amount of aluminum sulphate.

After the application of the first solution the paper should be blotted, as one has time to use a blotter, with good advantage, though not necessarily with rapidity, inasmuch as the applied solution is absorbed by the paper very slowly for an aluminum sulphate solution is slow to sink in, and checks penetration in the second step, presently to be referred to, to a remarkable extent.

The citric, or tartaric acid is used so that the colloid A12(SO4)3.18H2O will be kept in solution, and acts also as a solvent for portions of the ink, such as aniline dye, thereby increasing erasure efiiciency. Other acids might be used but citric acid is the best.

The benzoic acid is used to keep the solution sterile for otherwise tartaric acid liquids are apt to form a fungous growth, and citric acid liquids spoil. Aluminum sulphate decreases penetration so much that formaldehyde can be used to advantage as an additional preservative. Any weak antiseptic might be used provided it would not cause discoloration.

The second step of the process consists in applying to the paper any of the alkaline bleaching agents commonly employed in ink erasure, such as, preferably sgmurn hyppghlgritg These bleaching agents are always applied in water solution. The bleaching agent acts not only to remove the stain but, in so far as the present process is concerned, it performs the additional function of acting as a precipitant to cause an abundant precipitation of aluminum hydroxide from sulphate, leavin 1n the remdvedforat least harmed by the acid and especially by the alkali. The first solution will only affect the surface of the paper, or the part of the paper immediately adjacent its surface, for the solution absorbs slowly and will be removed by blotting before it has opportunity to thoroughly saturate the paper. In any event, the first solution being a more or less acid solution will slightly affect the sizing in the surface portion of the paper. The injury to the sizing is effected especially by the alkaline solution and it is the removed or harmed sizing in the paper which is replaced by the precipitated aluminum hydroxide, thus restoring the surface of the paper to its normal condition. The second step of the process, or the application of the alkali, should be a relatively quick step which may be gauged by the complete eradication of the ink or stain.

The third step of the process consists in the reapplication to the paper of the solution first applied in order to obtain a neutral, or near neutral, final state. It is also desirable to blot the paper for replacing the swim has'bee'n vvvvvv WWW A from sized papgrs hich includes the step of applying to the paper a water solution of an acid paper immediately after the application for any excess of acid may .dissolve out the freshly precipitated aluminum hydroxide. This third step of the process is not absolutely necessary although very desirable if the paper is to be immediately written upon, and if it is desired to retain, in so far as possible, the precipitate in the paper. a

I claim: 1. The process of chemical ink or stain erasur which will maintain an alumihfim s alt ifi solution and act as a solvent for portions of the ink, an aluminum salt which when reacted with an alkaline bleaching agent will precipitate aluminum hydroxide, and thestep of applying to the paper an alkaline blea'fiifig""a"giit'fj"water solution, said b leachih'f a'ger ft bbeiiig of a type capable of eradicating ink or stain and causing a precipitation of aluminum hydroxide from said aluminum salt wherebyv the ink or stain will be removed and said reaction product from said salt will be left precipitated in the paper.

2. The process of chemical ink or stain erasure from sized papers which includes the step of applying to the paper a water solution of an acid which will maintain an aluminum salt in solution and act as a solvent for portions of the ink, an aluminum salt which when reacted with an alkaline bleaching agent will precipitate aluminum hydroxide, the step of applying to the paper an alkaline bleachingagent in water solution, said bleaching agent being of a type capable of eradicating ink or stain and causing a precipitation of aluminum hydroxide from said aluminum salt whereby the ink or stain will be removed and said reaction product from said salt will be left precipitated in the paper, and neutralizing by application to the paper of the solution first mentioned.

3- The process of chemical ink or stain erasure from sized papers which comprises the step of applying to the paper a composition comprising a water solution of an acid of the group consisting of citric acid and tartaric acid and an aluminum salt of the group consisting of aluminum sulphate, ammonium alum and aluminum double sulphates and the step of applying to the paper an alkaline bleaching agent in water solution, said bleaching agent being of a type capable of eradicating ink or stain and causing a precipitation of aluminum hydroxide from said aluminum salt whereby the ink or stain will be removed and said reaction product from said salt will be left precipitated in the paper.

The process of chemical ink or stain erasure from sized papers which comprises the step of applying to the paper a composition comprising a water solution of an acid of the group consisting of citric acid and tartaric acid and an aluminum salt of the group consisting of aluminum I 

